The present invention relates to cellular radio communications, and more particularly, to the reporting and handling of cell status messages from a radio base station. The invention finds one example application in Wideband Code Division Multiple Access (WCDMA) communications systems.
Direct Sequence Code Division Multiple Access (DS-CDMA) allows signals to overlap in time and frequency so that CDMA signals from multiple users simultaneously operate in the same frequency band or spectrum. In principle, a source information digital data stream to be transmitted is impressed upon a much higher rate data-stream generated by a pseudo-random noise (PN) code generator. This combination of a higher bit rate code signal with a lower bit rate information stream xe2x80x9cspreadsxe2x80x9d the bandwidth of the information data stream. Each information data stream is allocated a unique PN or spreading code (or a PN code having a unique offset in time) to produce a signal that can be separately received at a receiving station. From a received composite signal of multiple, differently-coded signals, a PN coded information signal is isolated and demodulated by correlating the composite signal with a specific PN spreading code associated with that PN coded information signal. This inverse, de-spreading operation xe2x80x9ccompressesxe2x80x9d the received signal to permit recovery of the original data and at the same time suppress interference from other users.
Wideband CDMA systems contain one or several radio frequency carriers. Each radio frequency carrier contains a number of spreading codes which may be allocated to provide different data rates to satisfy different mobile user requirements. Some of those spreading codes are used for traffic channels and some are used for common control channels such as random access channels, paging channels, broadcast channels, etc. In order to provide flexibility in how bandwidth and other radio resources are allocated in wideband CDMA systems, a xe2x80x9clogicalxe2x80x9d cell is defined. Such a logical cell may be allocated more than one radio frequency carrier thereby permitting resources associated with different carriers belonging to the same cell to be allocated, for example, to a single mobile station requiring a high bit rate connection. The additional carrier(s) effectively provide more traffic channels.
One example of a wideband CDMA system is the universal mobile telecommunications system (UMTS) 10 shown in FIG. 1. A representative, circuit-switched, external core network, shown as a cloud 12 may be for example the public switched telephone network (PSTN) and/or the integrated services digital network (ISDN). Another circuit-switched, external core network may correspond to another-Public Land Mobile radio Network (PLMN) 13. A representative, packet-switched, external core network shown as cloud 14 may be for example an IP network such as the Internet. The core networks are coupled to corresponding network service nodes 16. The PSTN/ISDN network 12 and other PLMN network 13 are connected to a circuit-switched core node (CSCN) 18, such as a Mobile Switching Center (MSC), that provides circuit-switched services. The UMTS 10 may co-exist with an existing cellular network, e.g., the Global System for Mobile Communications (GSM). The packet-switched network 14 is connected to a packet-switched core node (PSCN), e.g., a General Packet Radio Service (GPRS) node 20 tailored to provide packet-switched type services in the context of GSM which is sometimes referred to as the Serving GPRS Service Node (SGSN). Each of the core network service nodes 18 and 20 connects to a UMTS terrestrial radio access network (UTRAN) 24 over a radio access network interface. The UTRAN 24 includes one or more radio network systems (RNS) 25 each with a radio network controller (RNC) 26 coupled to a plurality of base stations (BS) 28 and to the RNCs in the UTRAN 24.
Preferably, radio access over the radio interface in the UMTS 10 is based upon wideband, Code Division Multiple Access (WCDMA) with individual radio channels allocated using CDMA spreading codes which may each include both a channelization code and a scrambling code. Of course, other access methods may be employed like the well known TDMA access used in GSM. WCDMA provides wide bandwidth for multimedia services and other high transmission rate demands as well as robust features like diversity handoff and RAKE receivers to ensure high quality communication service in a frequently changing environment. Each mobile station is assigned its own spreading code in order for a base station 28 to identify transmissions from that particular mobile station. The mobile station also uses its own spreading code to identify transmissions from the base station either on a general broadcast or common channel or transmissions specifically intended for that mobile station. That spreading code distinguishes the spread signal from all of the other transmissions and noise present in the same area.
Different types of control channels are shown bridging the radio interface. For example, in the forward or downlink direction, there are several types of common control channels including a general broadcast channel (BCH), (there is only one broadcast channel per cell), a paging channel (PCH), and a forward access channel (FACH). In the reverse or uplink direction, a random access channel (RACH) is employed by mobile stations whenever access is desired to perform location registration, call origination, page response, and other types of access operations.
In general, each radio controller includes a memory coupled to data processing circuitry that performs numerous radio and data processing operations required to perform its control function and conduct communications between the RNC and other entities such as the core network service nodes, other RNCs and base stations. Data processing circuitry may include any one or a combination of suitable programmed or configured general purpose computer, microprocessor, microcontroller, dedicated logic circuitry, DSP, ASCI, etc. The base station similarly includes data processing in control circuitry, which in addition performs processing operations relating to communications with the RNC, performs a number of measurements in control operations associated with radio base station equipment. Data processing, memory, and transceiving circuitry is employed in each mobile station. The mobile station also includes a user interface with a speaker, microphone, keypad, display, and is typically powered by a battery.
Each base station shown FIG. 1 may include one or more physical sectors, and each sector provides coverage for a certain geographical area associated with the base station. Referring to the example in FIG. 2, each of three sectors 1xe2x80x943 has a corresponding antenna(s), transceiving hardware, and data and signal processing hardware to permit wideband-CDMA communications with mobile stations. In the present invention, each sector is mapped to one or more logical cells, and each cell may have one or more radio frequency carriers. For the example in FIG. 2, each sector includes four carriers f1-f4. Cell 1 is mapped to a base station sector with cell carriers f1 and f2; cell 2 is mapped to cell carrier f3; and cell 3 is mapped to cell carrier f4. Neighboring cells can also have the same carriers.
Further understanding of the cell definition in the present invention is outlined in the example illustration of potential components of a single base station cell in FIG. 3. The cell includes a primary carrier and zero or more secondary carriers that primarily provide additional traffic channels. Each carrier can encompass a wide frequency band, e.g., 5 MHz, in a WCDMA system. The primary carrier of a cell has one primary spreading code and zero or more secondary spreading codes. (A spreading code may include both a scrambling code and a channelization code; however, the details of specific CDMA codes are not essential to understanding of the invention). Each secondary carrier of a cell (if any) has one or more secondary spreading codes. The number of secondary carriers in this definition may differ in the downlink direction (base station-to-mobile station) from the uplink direction (mobile station-to-base station). Associated with each channelization code is one or more physical channels, such as a common control physical channel (CCPCH), that may be mapped to one or more transport channels such as a broadcast channel (BCH). Other example, non-limiting channel mappings are shown and defined in FIG. 3.
The definition of such a logical cell provides considerable flexibility in allocation of various radio resources to mobile station connections that require different services like speech, email, web browsing, downloading files from the web, video, etc. As mentioned above, a plural carrier cell can provide higher bit rate opportunities to better service a wide range of mobile connections. However, this flexibility and capability adds some complexity with respect to identifying various resource status and capability changes at each base station.
The radio network controller (RNC) must allocate and monitor resources like spreading codes (corresponding to various channels) based on this multi-carrier cell definition. If resources are identified in the context of the cell, as they often are, they may be unique only within the context of that cell. Consequently, the cell resource identifier is not unique outside of the context of that cell, and therefore, presents a potential ambiguity to the base station. For example, FIG. 4 shows a simplified, example situation where two sectors 1 and 2 of a base station are each configured with three cells. The three cells of the base station sector 1 are identified with cell IDs 1, 2 and 3. The three cells of base station sector 2 are identified with cell IDs 4, 5, and 6. Unfortunately, every one of the six cells identifies a first channel resource with the same channel ID xe2x80x9c1.xe2x80x9d Thus, the channel resource identifier is cell unique, but not unique outside of that cell. A base station status message that simply indicates a resource capability change, e.g., a decrease in channel capacity or an error or fault in the transceiver board assigned to that channel, cannot be resolved with certainty by the RNC using only the channel resource identifier. In short, the RNC does not know to which cell the cell resource status belongs. As a result, it may be necessary for the RNC to take remedial action, e.g., a reset or restart operation, for all resources in a cell or even in the entire base station.
In the present invention, a resource indication message sent from the base station to the radio network control node includes a cell resource identifier and indicates a status of a particular resource (e.g., a radio channel resource) within that cell. To eliminate any ambiguity at the radio network control node that might be created if cell resource identifiers are not unique outside of the cell, the cell resource identifier is specifically correlated with a corresponding cell identifier in the resource indication message. Non-limiting examples of cell identifier/cell resource identifier associations are described below in the context of a xe2x80x9cservice impactingxe2x80x9d part of a resource status indication message (RSIM) in a wideband-CDMA cellular radio communications system.